Filling systems incorporated in bottling machines and defining respective filling stations are known.
More precisely, the filling station is fed with empty containers and provides containers filled with the pourable food product.
The filling station substantially comprises a carousel conveyor rotating about a rotation axis, a tank containing the pourable food product and positioned on the carousel or externally thereto, and a plurality of filling valves which are fluidically connected with the tank and are supported by the carousel conveyor in a radially external position with respect to the rotation axis of the carousel conveyor.
In greater detail, the valves are displaceable between respective open positions in which they allow the flow of pourable product within the respective containers, and respective closed positions in which they prevent the pourable product from flowing within the respective containers.
The carousel conveyor is provided with a plurality of support elements for the containers provided to arrange container filling mouths in positions below the respective valves and handle the containers along an arc-shaped path about said rotation axis integrally with the respective valves.
The tank is fluidically connected with the filling valves by means of a plurality of ducts, along each of which magnetic flowmeters are interposed to measure, when the respective filling valves are arranged in open positions, the flow rates of fluid by which the containers are filled.
The measurement of the flow rate performed by the magnetic flowmeters is used to control the movement of the filling valves between the respective open and closed positions, so as to fill the containers with a desired amount of pourable food product.
In greater detail, the magnetic flowmeters create a magnetic field in a direction radial to the axis of the duct and detect an output voltage proportional to the speed and, therefore, to the flow rate of the pourable product.
More precisely, the pourable product has an own electric conductivity, substantially due to the fact that it contains dissociated ions, and therefore gives rise to electric currents when it passes through the magnetic field generated by the electric conductivity flowmeter.
These currents are detected by means of a voltage measurer, which inevitably varies the measurement of the flow rate performed by the flowmeter mainly due to its internal resistances generating a measurement error.
Recently, the need has developed in the sector for containers filled with osmotised water, i.e. water substantially free of dissolved salts and having a very low electric conductivity, for example lower than 15 μS.
The Applicant has noted that when the electric conductivity of the pourable product reaches such low values, the measurement error introduced by the magnetic flowmeter in the measurement of the flow rate is particularly relevant and sometimes on the same order of magnitude of the flow rate.
Therefore, the measurement of the flow rate performed by the flowmeter results in these cases poorly reliable, generating problems in the precision and in the repeatability of the filling of the container.
The need is felt for measurements of the flow rates of pourable products with especially low electric conductivity, such as for example osmotised water, in a simple and cost-effective manner and reducing the presence of mobile parts as much as possible.